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| Millikan's oil drop apparatus. |
— Sir Arthur Eddington (1882 – 1944). Petrus Macinnius
Every process can
be interpreted either in terms of corpuscles or in terms of waves, but on the
other hand it is beyond our power to produce proof that it is actually
corpuscles or waves with which we are dealing, for we cannot simultaneously
determine all the other properties which are distinctive of a corpuscle or of a
wave, as the case may be.
— Max Born (1882 – 1970), Atomic Physics,
7th edition, Blackie, 1964, 97.
The probable
lifetime of a radioactive atom is less predictable than that of a healthy
sparrow.
— Erwin Schrödinger (1887 – 1961), quoted by Max Perutz, Nature, 9/4/1987, 555.
— Three quarks for Muster Mark!
Sure he hasn’t got much of a bark
And sure any he has it’s all beside the mark.
But O, Wreneagle Almighty, wouldn’t un be a sky of a lark
To see that old buzzard whooping about for uns shirt in the dark
And he hunting round for uns speckled trousers around by Palmerston Park?
Hohohoho, moulty Mark!
You're the rummest old rooster ever flopped out of a Noah's ark
And you think you're cock of the wark.
Fowls, up! Tristy's the spry young spark
That'll tread her and wed her and bed her and red her
Without ever winking the tail of a feather
And that's how that chap's going to make his money and mark!
— James Joyce, Finnegans Wake, Faber standard edition,
383.
The experiments
discussed in this paper were undertaken in the hope of gaining some information
as to the nature of the Cathode Rays. The most diverse opinions are held as to
these rays; according to the most unanimous opinion of the German physicists they
are due to some process in the aether to which … no phenomenon hitherto
observed is analogous: another view of these rays is that … they are wholly
material, and that they mark the paths of particles of matter charged with
negative electricity. It would seem at first sight that it ought not to be
difficult to discriminate between views so different, yet experience shows that
this is not the case, as amongst physicists who have most deeply studied the
case can be found supporters of either theory.
The
electrified-particle theory has for purposes of research a great advantage over
the aetherial theory, since it is definite and its consequences can be
predicted; with the aetherial theory it is impossible to predict what will
happen under any given circumstances, as on this theory we are dealing with
hitherto unobserved phenomena in the aether, of whose laws we are ignorant.
— Sir Joseph John Thomson (1856 – 1940), Phil.
Mag. S.5 Vol. 44, No. 269, Oct
1897, 293.
Ever since 1930,
when the discovery of the neutron made it plain that the nuclei of atoms were
built of protons and neutrons, physicists have been trying to form a picture of
the structure of the nucleus. The same task for the rest of the atom was completed
in the first quarter of this century. We were able to understand in detail how
the electrons move under the attraction of the nucleus, and how their motion is
influenced by their mutual repulsion.
To achieve such
an understanding requires three steps: First, we must know the forces between
the particles. Second, we need to know the mechanical laws which govern their
motion under the influence of these forces. Third, we need in most cases a
simplified picture, or model, from which to start. Once we have the first two
ingredients, we could in principle write down a set of mathematical equations
whose solutions would tell us all about the atom, or about the nucleus. In the
simplest possible atoms, like that of hydrogen, in which there is only one
electron, or in the simplest compound nuclei, like the deuteron, which contains
only one proton and one neutron, such equations can be written down and solved
without difficulty. However, for more complicated structures this head-on
attack becomes much harder and soon exceeds the capacity even of modern
electronic computers.
— Sir Rudolf Peierls (1907 – 1995), ‘Models of the Nucleus’, Scientific American, June 1959.
Physics is
becoming so unbelievably complex that it is taking longer and longer to train a
physicist. It is taking so long, in fact, to train a physicist to the place
where he understands the nature of physical problems that he is already too old
to solve them.
— Eugene Paul Wigner (1902 – 1995).
The sciences do
not try to explain, they hardly even try to interpret, they mainly make models.
By a model is meant a mathematical construct which, with the addition of
certain verbal interpretations, describes observed phenomena. The justification
of such a mathematical construct is solely and precisely that it is expected to
work.
— John von Neumann (1903 – 1957), quoted by James Gleick, Chaos 273.
The uncertainty
principle refers to the degree of indeterminateness in the possible present
knowledge of the simultaneous values of various quantities with which the
quantum theory deals; it does not restrict, for example, the exactness of a
position measurement alone or a velocity measurement alone. Thus suppose that
the velocity of a free electron is precisely known, while the position is
unknown. Then the principle states that every subsequent observation of the
position will alter the momentum by an unknown and undeterminable amount such
that after carrying out the experiment our knowledge of the electronic motion
is restricted by the uncertainty relation. This may be expressed in concise and
general terms by saying that every experiment destroys some of the knowledge of
the system that was obtained by previous experiments. This formulation makes it
clear that the uncertainty relation does not refer to the past; if the velocity
of the electron is first known and the position then exactly measured, the
position for times previous to the measurement may be calculated. Then for
these past times DpDq
is smaller than the usual limiting value, but this knowledge of the past is of
a purely speculative character, since it can never (because of the unknown
change in the momentum caused by the position measurement) be used as an
initial condition in any calculation of the future progress of the electron and
thus cannot be subjected to experimental verification. It is a matter of
personal belief whether such a calculation concerning the past history of the
electron can be ascribed any physical reality or not.
— Werner Karl Heisenberg (1901 – 1976), The
Physical Principles of the Quantum Theory, Dover Books.
In order to make
progress we had to produce a supply of artificial bullets. And that was the
next step and it was made in Lord Rutherford’s laboratory in Cambridge in 1932.
There is no difficulty in securing a supply of bullets. In any electrical
discharge lamp, such as a neon sign, these atomic bullets are moving about in
millions. If the lamp is filled with helium or hydrogen, and if a suitable hole
is made in the side of the tube, a stream of suitable particles will emerge.
The next step is to speed them up, and to do this we built an atomic gun. This
consisted of four of those glass cylinders which used to be used for petrol
pumps. The air inside was pumped out, our bullets were fired in at the top and
a very high electrical voltage was applied there. Now, since our bullets carry
an electrical charge they are repelled from the top plate and, shooting down
through the gun, they emerge with a speed such that they would cross the
Atlantic in less than a second.
We produced in
this way a very intense stream of fast hydrogen atoms, and were at last
rewarded by discovering that these bullets were even more potent than the
natural atomic bullets from radium. We were able to show that if the lightest
metal, lithium, is bombarded with them some of the lithium atoms are split up
into two atoms of helium. If the metal boron is bombarded, it splits up into
three atoms of helium, and so on.
Most interesting
of all, perhaps, was the discovery that we could use these atomic bullets or
protons to produce the unstable or radioactive forms of the common elements
which had just been discovered by Professor Joliot [Joliot-Curie] … We can
produce, for example, radioactive forms of sodium, iron, or iodine. And having
produced them we found that our biological colleagues were eager to use them
[as tracers] …
Atom-shattering
has therefore become a popular pursuit until the present war directed the
attention of British and American physicists to other, more urgent, work.
— Sir John Douglas Cockcroft (1897 – 1967), ‘Shattering the atom’, a BBC radio
talk, given in 1942.
As physics has
advanced, it has appeared more and more that sight is less misleading than
touch as a source of fundamental notions about matter. The apparent simplicity
in the collision of two billiard balls is quite illusory. As a matter of fact
the two billiard balls never touch at all; what really happens is inconceivably
complicated, but it is more analogous to what happens when a comet penetrates
the solar system and goes away again than to what common sense supposes to
happen.
— Bertrand Russell (1872 – 1970), The ABC
of Relativity, 1925.
… we shall assume that the cluster of electrons is formed by the successive binding by the nucleus of electrons initially nearly at rest, energy at the same time being radiated away.
This will go on
until, when the total negative charge of the bound electrons is numerically
equal to the positive charge on the nucleus, the system will be neutral and no
longer able to exert sensible forces on electrons at distances from the nucleus
great in comparison with the dimensions of the orbits of the bound electrons.
On account of the
small dimensions of the nucleus, its internal structure will not be of sensible
influence on the constitution of the cluster of electrons, and consequently
will have no effect on the ordinary physical and chemical properties of the
atom. The latter properties, on this theory, will depend entirely on the total
charge and mass of the nucleus; the internal structure of the nucleus will be
of influence only on the phenomena of radioactivity.
— Niels Henrik David Bohr (1885 – 1962).
… the nitrogen
recoil atom … should produce not more than about 10,000 ions, and have a range
in air at N.T.P. of about 1.3 mm. Actually, some of the recoil atoms in
nitrogen produce at least 30,000 ions. In collaboration with Dr. Feather, I
have observed the recoil atoms in an expansion [Wilson Cloud] chamber, and
their range, estimated visually, was sometimes as much as 3 mm at N.T.P.
I know no one who
had finer experimental sense [than] my old Professor, Sir J. J. Thomson, at
Cambridge. Yet he was quite hopeless with his hands. But when he worked with
his famous assistant Everett, who could realise all the experiments which “J.J.”
first performed in his head, as it were, an outstandingly effective combination
was achieved. It was by that famous partnership that the subject of electronics
was founded.
In my own case, I
think I can claim that, by taking lessons from Everett, I became a little more
proficient in soldering and glass-blowing than my Professor; but it has always
been my experience that my assistants could beat me easily at both.
— Sir Edward Victor Appleton (1892 – 1965), Science
for its own sake: 1956 Reith Lectures.
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